Wireless telegraphy.



No. 7l6,203. I Patented D'ecflfi, I902;

' L. m: FOREST & E. H. SMYTHE.

T WIRELESS TELEGBAPHY. (Application filed Sept. 1, 1900.) (No ModeL).

m: "cams PETERS scum-um mm. WASHINGYON. n: c.

UNITED STATES PATENT J rFicE;

LEE DE FOREST, OF CHICAGO, AND EDWIN H. SMYTI-IE, OF FBEEPORT, ILLINOIS.

WIRELESS TELEGRAPHY.

SPECIFICATION forming part of Letters Patent No. 716,203, dated December16, 1902.

Application filed September 1, 1900. Serial No. 28,722. (No model.)

To all rah/0111, it may concern:

Be it known that we, LEE DE FOREST, residing at Chicago, in the countyof Cook, and ED- WIN H. SMYTHE, residing at Freeport, in the county ofStephenson, State of Illinois, citizens of the United States of America,have invented certain new and useful Improvements in WirelessTelegraphy, of which the following is a specification.

Our invention relates to improvements in wireless telegraphy, andparticularly to an improved conductor of variable resistance adapted andintended for use in the circuit of the receiving apparatus of awireless-telegraph system, the variation of the resistance of saidconductor being caused by the passage of electric waves generated by asuitable transmitting apparatus.

The object of our invention is to provide a conductor which shall notonly have the variation of resistance referred to, but which shall be soconstructed as to be extremely sensitive, capable of operating at apractically unlimited speed, and practically permanent in its workingcapacity.

The invention may be embodied in various forms, all operating onsubstantially the same principle; but in the drawings accompanying athis specification and forming a part of this application we have showna single simple apparatus including the variable-resistance conductor inone of the forms in which we have made and thoroughly tested it.

In the drawings referred to, Figure 1 is a diagrammatic representationof a receiving circuit in combination with the usual aerial conductor orreceiver which is the initial element in the receiving apparatus, andFig. 2

is a transverse section of the variable-resistance conductor shownpartly in elevation and partly in vertical section in Fig. 1.

In the views, A is a local circuit, including a suitable battery orother source of electromotive forceB and a telephone-receiver or othersignaling device 0, one link in the circuit being thevariable-resistance conductor,

which will presently be described in detail.

D is the ordinary aerial conductor, having a height suitable to theconditions of its use, this conductor being in electrical connectionwith the local circuit A and also connected to ground or to suitablecapacity by means of cuit. Choke-coils F F are interposed in the localcircuit between the aerial conductor D and the signaling device on theone hand and between the aerial conductor and the battery or source ofelectric supply on the other hand, it being essential that theconnection of the conductor E with the local circuit shall be betweenthe corresponding choke-coil'F and the aerial conductor. Thevariable-resistance conductor is placed in the local circuit between theaerial conductor D and the groundwire E, and in the form shown in thedrawings it includes two preferably metallic electrodes G G, which maybe plane-faced bars overlapping each other, as shown, or may have suchother form and relative position as will bring their opposed faces ofsuitable area into approximately parallel positions of slightseparation. These electrodes may be held in their proper relation by anysuitable means, and the space between them is filled by any suitablefluid, so held in place as to maintain a uniform tension.

In our experiments thus far we have found that liquids interposedbetween the electrodes give the most satisfactory results, for thereason that any liquid so interposed may be used for a considerableperiod of time without perceptible deterioration of its operativecapacity, its maintenance in a stable or constant condition being thusassured without the use of anyapparatus for that purpose. Furthermore,we find that the liquid interposed between the electrodes is much morepermanent in its operation than an interposed fiilm of vapor, which byreason of evaporation would require constant renewal. In thevariableresistance conductor shown in the drawings the electrodes G Gare supported by a suitable vessel H, containing a liquid in which theelectrodes are immersed, the space between the overlappihg faces of thetwo electrodes being thereby filled with the liquid,

which, being interposed in series between the electrodes, forms theconnection between the electrodes, and thus completes the conductor.

Under ordinary conditions when the receiving apparatus thus shown anddescribed is not in operation the current generated by the local batterypasses through the circuit including the signaling device, thechokecoils, and the variable-resistance conductor, no materialresistance to the passage of the current being offered by thechoke-coils or by the variable-resistance conductor, the resistance ofwhich under such conditions is at its lowest limit. Upon the receipt ofan electric impulse through the aerial conductor the resistance of thechoke-coils to the passage of the wave forcesit to pass by Way of theground connection E to the ground, and thus insures its passage throughthe variable-resistance conductor. The passage of the wave through theconductor greatlyincreases its resistance, and since thevariable-resistance conductor is in the local circuit this change ofresistance is indicated by the telephone or other signaling device,which is also in the local circuit. Our use of the variable-resistanceconductor having the construction shown and described has beensufficient to demonstrate not only its extreme sensitiveness, but alsoits remarkable rapidity of action. The variation of resistance of theconductor due to -the passage of successive electric impulses is plainlymarked, no matter how rapidly the impulses may succeed each other, and,in fact, the onlylimit to the distinct indication of the passage ofsuccessive impulses is the recording capacity of the signaling device orthe capacity of the senses for distinguishing separate signals. Thiscapacity for rapid repetition of the variation of resistance in theconductor is a consequence, as well as a demonstration, of the fact thatthe passage of the electrical impulse through the liquid interposedbetween the eloctrodes produces no change of conditions therein, exceptsuch as is instantaneously and automatically counteracted, the conductorbeing thus restored to its condition of normal resistance immediatelyafter the passage of. each impulse. This rapidity of action of thevariable-resistance conductor is of great practical importance, for thereason that it makes it possible to distinguish perfectlybetweenimpulses generated with predetermined frequency at atransmittingstation and other electrical impulses following each other at adifferent rate. This apparatus operates equally well, therefore,undervarying electricalconditions, its action being perfect in the presenceof atmospheric electric disturbances in the sense that the impulses froma transmitting-station have a uniform frequency of impulse,whereby theymay be readily distinguished from other and accidental impulses. In factthe signaling device may be placed iuasuitablytuned circuit and may be.thus made to respond automatically to similarly-tuned impulses and to noothers, the signaling device being thus made to automatically selectimpulses transmitted at a predetermined frequency.

In speaking of the interposed liquid as permanent orstable and asunchangedby the passage through it of electric impulses we have had inmind the evident fact that it is perfectly operative as a means ofindicating the passage of a great number of successive impulsescoveringa considerable period of time. We have nevertheless found itdesirable to occasionally change or renew the liquid, and this may beaccomplished by flowing a current of liquid through the vesselcontaining the electrodes or in any other simple and effective way. Inthe drawings hereinbefore referred to the electrodes are shown in acondition of immersion in the liquid, and this is one simple and evidentway of securing the constantpresence of the interposed liquid betweenthe electrodes. The best way, however, in which We have contemplatedmaintaining the constant pressure of the interposed liquid between theelectrodes is to employ a suitable porous material constantly saturatedwith the liquid and to interpose such porous material between theelectrodes. Our experiments have demonstrated that such arrangementresults in the production of the best effects, and our theory is thatthe porous material operates to retain the particles of metal which aredetached from one electrode by the-passage of the current and carriedtoward the other electrode and to prevent such metallic particles frombecoming precipitated or from settling to the bottom of the vessel orreceptacle containing the liquid in which the electrodes are immersed.

We have found in our experiments that in the use of an apparatusembodying the principles above set forth and wherein are employedmetallic electrodes a deposit occurs on the negative electrode from thepositive electrode, even where the electrodes are immersed inchemically-pure water, and therefore we are confirmed in our theory thatthe interposition of the porous body between the exposed or juxtapositedsurfaces-of the electrodes forms a support or retainer for the metallicparticles which would otherwise be transferred from one and depositedupon the other of the electrodes.

The liquid which we have used in our experiments and which we have foundto be perfectly satisfactory in its operation is water; but we do notintend to limit our invention to the use of this particular liquid, asothers equally desirable or even more desirable may be determined byfurther experiment. It will be understood, of course, that we do notlimit the invention to the use of any simple liquid, since this term isevidently broad enough to include chemical solutions, dilute orotherwise, as well as liquids holding in suspension particles of anynature which may be found to contribute to the effective operation ofthe interposed film.

Then the electrodes are immersed in a liquid contained in an openvessel, as shown in the drawings,it is desirable that all those parts ofthe electrodes except the actually overlapping surfaces or juxtaposedportions be varconcerned.

lent results from the use of two electrodes,

any possibility of short-circuitingthrough the liquid. In referring tothe overlapping or opposed surfaces of the electrodes we do not intendto impose any limitation so far as the extent of area of the opposedsurfaces is In fact, we have obtained excelone having a plane surface ofconsiderable area and the other having a thin or \l-shaped edge parallelto the plane surface of the first. This form is conveniently adjustableand has apparently exactly the same operation as the form including twooverlapping plane-faced bars. We have only illustrated one simple form,for the reasonthat we do not desire or intend to make the shape orextentof the opposed surfaces of the electrodes an essential element of ourinvention.

We claim as new and desire to secure by Letters Patent- 1. In a receiverfor electricaloscillations, the combination with a suitable receptacleadapted to receive a liquid, of electrodes supported in said receptacleand suitably separated from each other, the surfaces of said electrodesbeing covered with insulating material except at juxtaposited points,the liquid contained in saidreceptacle being interposed between saidelectrodes and forming a normally closed series electrical connectiontherebetween,as and for the purpose set forth.

2. Ina receiver for electrical oscillations, the combination with areceptacle adapted to receive a liquid, of suitably-separated electrodessupported in said receptacle in position to be immersed in the liquidcontained therein, the surfaces of said electrodes being covered withinsulating material except at juxtaposited points, whereby a body ofliquid is constantly maintained in series relation between the exposedjuxtaposited points or surfaces of said electrodes to completeelectrical connection therebetween, as and for the purpose set forth.

3. In a receiver for electrical oscillations, the combination with twosuitably-separated electrodes having opposed or juxtapositedconducting-surfaces, of a layer of porous material saturated with asuitable liquid, said porous material beinginterposed between and inseries with the conducting exposed surfaces of said electrodes,andoperating to electrically connect said surfaces, as and for thepurpose set forth.

4:. In a receiver for electrical oscillations,

. suitably-separated electrodes having juxtaposited exposedconducting-surfaces, a liquid body interposed between such surfaces,

and means for maintaining the metallic particles detached from theelectrodes by the pas: sage of the current suspended in said liquidinthe space between the exposed surfaces of said electrodes, as and forthe purpose set forth.

5. In a receiver for electrical oscillations,

the combination with suitably-separated electrodes adapted to receive abody of liquid between the exposed surfaces thereof, means formaintaining said body of liquid between said surfaces, and means forretaining the metallic particles held in suspension in said liquidbetween said surfaces, as and for the purpose set forth.

6. In a receiver for electrical oscillations, a local circuit,electrodes suitably separated from each other and arranged in saidcircuit, a receiving-conductor, a ground or capacity connectiontherefor, said electrodes being also included in said ground or capacityconnection, said electrodes having a body of liquid interposed betweenthe exposed surfaces thereof, and means for retaining the metallicparticles detached from said electrodes from being precipitated, wherebyelectrical connection is maintained between said electrodes to normallyclose said local circuit, as

and for the purpose set forth.

7 In a receiver for electrical oscillations, a local circuit, electrodessuitably separated from each other and arranged in said circuit, areceiving-conductor, a ground or capacity connection therefor, saidelectrodes being also included in said ground or capacity connection,and a saturated porous body interposed in series between the exposedsurfaces of said electrodes, as and for the purpose set forth.

8. In a receiver for electrical oscillations, the combination withsuitably-separated electrodes having exposed juxtaposited surfaces, ofmeans for maintaining metallic particles in suspension between suchexposed juxtaposited surfaces, as and for the purpose set forth.

9. In a receiver for electrical oscillations,

a local circuit, electrodes suitably separated from each other andarranged in said circuit,

a receiving-conductor, a ground or capacity connection therefor, saidelectrodes being also included in said ground or capacity connection,and means for maintaining metallic particles in suspension between theexposed surfaces of said electrodes to normally close the circuittherebetween, as and for the purpose set forth. I

10. In a receiver for electrical oscillations, a local circuit,electrodes suitablyseparated from each other and arranged in saidcircuit, a receiving-conductor, a ground or capacity con nectiontherefor, said electrodes being also, included in said ground orcapacity connection, and a porous body interposed in series.

between the exposed surfaces of said elec-. trodes, as and for thepurpose set forth.

11. In a receiver for electrical oscillations,

a local circuit, electrodes suitably separated I from each other andarranged in said circuit,

a receiving-conductor, aground or capacity. connectiontherefor, saidelectrodes being also included in said ground or capacity connection, areceptacle adapted to receive aliquid,

said electrodes being immersed in said liquid, and a porous bodyinterposed in series between said electrodes, as and for the purpose setforth.

12. In a receiver for electrical oscillations, a local circuit, a signaldevice, and a resistance device, included in said local circuit, saidresistance device comprising suitablyseparated electrodes having aninterposed body of liquid between the exposed surfaces thereof, meansfor maintaining or holding in suspension metallic particles in saidliquid, in combination with a receiving-conductor, a ground or capacityconnection for said conductor, said ground or capacity connectionincluding said resistance device, and means for preventing theelectrical oscillations in said receiving-conductor and its connectionfrom traversing said local circuit, as and for the purpose set forth.

13. Ina receiver for electrical oscillations, a local circuit, a signaldevice arranged therein, a receptacle adapted to contain a liquid orfluid, electrodes arranged in said receptacle and suitably separatedfrom each other, a porous body interposed in series between saidelectrodes to complete electrical connection between said electrodes,said electrodes being included in said local circuit, areceiving-conductor, a grounded or capacity connection therefor, saidelectrodes being also included in said grounded or capacity connection,as and for the purpose set forth.

14:. In a receiver for electrical oscillations, a local circuit, asignal device included therein, electrodes included in said circuit andsuitably spaced apart, said electrodes adapted to receive a porous bodysaturated with a suitable fluid or liquid between the opposed surfacesthereof to complete electrical connection therebetween, areceiving-conductor, a grounded or capacity connection therefor, saidelectrodes being also included in said grounded or capacity connection,and induction devices arranged in said local circuit, as and for thepurpose set forth.

15. In a receiver for electrical oscillations, the combinationwithsuitably-separated electrodes, a local circuit therefor, and meansfor confining the metallic particles in the space between saidelectrodes and comprising a fabric placed between said electrodes, asand for the purpose set forth.

In witness whereof we have hereunto set our hands, at Chicago, in thecounty of Cook and State of Illinois, this 29th day of August,

LEE DE FOREST.

EDWIN H. SMYTHE. Witnesses:

R. H. WILES,

OHAs. O. SHERVEY.

